TLC5958, the LED lights up, but the current cannot be measured...

风过琴弦

TLC5958, the LED lights up, but the current cannot be measured... [Copy link]

Now I can control which one to light up and the brightness, but it is not bright enough even when the brightness is set to the maximum. I want to measure the actual current, and something strange happens...

The LED was connected in series with a 10Ω resistor, and later a 51Ω resistor was added. No matter whether I used a multimeter or an oscilloscope, I could not see the voltage on the resistor. (The LED was clearly on, and there were times when it changed from bright to dark.) Not only was the voltage measured by the multimeter only about 0.3mV, I doubted whether it was interference or real voltage, but the oscilloscope could not see the waveform, from a few uS to mS. The LED switch was switched with a button, and no change was seen before and after.

I used the current range of the multimeter directly, but the Fluke F15 could not measure it. However, a multimeter given away for free by LiChuang Mall could measure 60mA. There is also a Fluke oscilloscope with a current range, which measured about the same number. However... If the current value is this, how could there be no waveform on the 10Ω resistor? That is a voltage of 600-700 mV. It is impossible not to see 60-70 mV.

Additional content (2024-1-5 22:55): ... I just changed a chip and it worked. It's just... I can control the light on and off from the register, and the brightness is adjustable. I always thought that the chip was not broken. But... Thank you for your help

qwqwqw2088

The LED is on, which can be measured with a multimeter.

mA level current can be measured with a multimeter, especially a Fluke meter.

Check if the measurement connection is connected.

If PWM control is used, the oscilloscope can also measure

haocede

I connected a 10Ω resistor in series with the ED, and later added a 51Ω resistor. I couldn't see the voltage on the resistor using a multimeter or an oscilloscope. (The LED was clearly on, and there were times when it changed from bright to dark.) Not only was the voltage measured by the multimeter only about 0.3mV, I doubted whether it was interference or real voltage, but the oscilloscope also couldn't see the waveform, from a few uS to mS. I couldn't see the change before and after the LED was switched on and off with a button.

chunyang

For PWM signals, a general multimeter may indeed have a large test error, but DC or low-frequency sinusoidal AC is no problem, after all, the multimeter has its specific application range. As for the oscilloscope not being able to see the waveform, it must be your operation is wrong.

lvxiafu

This current is too small, usually at the mA level, and cannot be measured by a multimeter.